Absolute Zero
'Fundamentals' Let's get down to the basic: before we start on what absolute zero means, we have to establish the fundamentals. One of the elementary concepts in physics and chemistry is that when a geven amount of gas is cooled, the molecules start to slow down. When they are heated, they will get excited and move around. The first image is one of hot molecules. As you can see, they are moving around rapidly. The second image is one of molecules moving very slowly; these are in a cold temperature. Well, have you ever wondered if there was ever a state in which molecules would just CEASE to move and stay still? Well, this is what absolute zero is here for. 'What is Absolute Zero?' According to the Third law of thermodynamics, Absolute zero is basically the lowest temperature on the scale. It is a temperature where a body can no longer release heat or energy to its surroundings. While there have been numerous attempts and people have come very close to reaching this point, the temperature is said to be unattainable in practice. This fact is also from the Third law of thermodynamics; It is impossible to reach the absolute zero temperature in a finite number os steps in a process.(235: Calle, Carlos) Absolute zero is measured as zero °K (Kelvin temperature), -273 ° C(Celcius), or -459 °F (Fareinheit). As stated above, absolute zero is said to be unattainable in practice. According to the Uncertainty Principle, there needs to be a small amount of residual motion (zero-point motion), even at absolute zero. Image obtained from www.pa.msu.edu. ''' Why Kelvin? Most Physicists use Kelvin to measure substances rather than Fareinheit or Celcius. The reason is at Kelvin, zero is where absolute zero is and at 100°K, air liquifies. While Celcius is useful for everyday purposes like knowing when water boils, it is much easier for physicists to use Kelvin to measure things. Here is a picture comparing Fareinheit and Kelvin: Image obtained from http://www.colorado.edu/physics/2000/bec/temperature.html 'How do we go about Reaching Absolute Zero? ' The answer to that is cryogenics! What are cryogenics? It basically is the study and use of substances in very cold temperatures. Anything below the temperature of -150°'C is considered within the field of cryongenics. Liquid helium is something that is often associated with Absolute zero because of its low temperature (4.2K), which can be produced by using cryostats. By evaporating helium, temperatures as low as 0.7 K can be reached. Temperatures even closer to absolute zero can be reached with helium using Adiabatic demagnetization. '''Adiabatic demagnetization This scary sounding word is one method used to come close to absolute zero. In order to go through with this procedure, we would first need a magnetic field. We put this field around a paramagnetic pole(basically something with a magnetic north and south pole)while it is being cooled by liquid helium. The field's properties will force the magnets to align together in one direction (pointing north), and when the field is removed, the little magnets resume their random arrangements. This procedure causes the thermal energy to fall, and results in temperatures as low as 0.002K. Using other substances, temperatures as low as 0.00001 K have been reached using this method. Image obtained from Encarta 2002 'My Famous Homies ' *German Physical Chemist Harmann Nernst was the one who proposed that absolute zero is impossible to reach: "Third Law of Thermodynamics: It is impossible to reach the absolute zero teperature in a finite number of steps of a process. He was awarded the Nobel Prize in 1920 for his discovery. *American Mechanical Engineer Samuel Collins: he was the one who designed cryostats, which are very well insulated vessels. * Canadian-American chemist William Giauque: in 1937, he developed teh method of thermodynamics in which magnetic fields align the ionic magnets of the substance. *Scottish physicist William Thomson (Lord Kelvin): created the Kelvin scale in 1851. Kelvin Temperature is defined by Tkelvin=tcelcius+273. For example: water boils at 100°C, so it boils at 373°K (100+273= 373 * Arno Penzias and Robert Wilson: the men who discovered that outer space was filled with radiation at the temperature of 2.73 K. They won the Nobel Prize for their discovery in 1964. 'Who came Close to Acheieving Absolute Zero?' Scientist have been able to cool substances to as low as .000001 Kelvin, and there are people that are trying to reach even closer limits to absolute zero right now as you are reading this web page, but here are some records that we have so far: *As of September 2003, the lowest temperature Bose-Einstein condensate achieved was 450 pK, or 4.5 × 10-10 K. This was performed by Wolfgang Ketterle and colleagues at the Massachusetts Institute of Technology. *As of February 2003, the Boomerang Nebula, with a temperature of 1.15 K, is the coldest place known outside a laboratory. The nebula is 5000 light-years from Earth and is in the constellation Centaurus. *As of November 2002, the coldest temperature produced was 100 pK during an experiment on nuclear magnetic ordering in the Helsinki University of Technology's Low Temperature Lab. (This information (the list) was obtained from Wikipedia: Absolute Zero) * Cornell and Wieman cooled a small sample of atoms down to only a few billionths (0.000,000,001) of a degree above Absolute Zero. 'Well, what does Absolute Zero say About Anything?' Well, Absolute Zero is one of the arguments scientists use to prove that the Big Bang happened. Theory has it that the heat of the Big Bang was diffused throughout the entire universe, so there is no place in the universe that is naturally lower than 2.73 Kelvin, to date.(Humans have achieved lower temperatures than 3°K, but that isn't considered natural.) Initially, our universe was very hot, but as time passed by (some 700,000 years), the universe began to spread out and cool down; This is why the temperature in space is so cold. Measurements of the temperature were made by the COBE satellite in 1989. The 2.73 Kelvin (rounded up to 3)Rule is called the "3 Degree Kelvin Background Radiation". Therefore, there are places in the universe where the molecules are moving in serious slow-mo, but are not absolutely motionless. For more information about this phenomenon, go to http://www.csep10.phys.utk.edu. The radiation is not completely uniform, as shown in this picture taken by the COBE satellite, but these differences are very small, showing fluctuations only about 1/100,000 deviations away from the average. The red parts show the areas that are hotter and the blue parts are the a little cooler than the average: Image obtained from http://csep10.phys.utk.edu/guidry/violence/bang2.html 'Physics Problems' While there are no problems on the physics regents that deal specifically with absolute zero, it is important that we know how to convert from Celsius to Kelvin and vice versa. Here are a few sample problems: # Convert 43°C to the Kelvin Scale. # Convert 40°K to the Celsius scale. Solutions: # Tkelvin=Tcelsius+273 so 43°C+273= 316°K. # Tkelvin=Tcelsius+273 therefore Tcelsius= Tkelvin-273, so 40°K-273= -233°C. 'Resources and references' 'Resources' # Lightman, Alan Great Ideads In Physics U.S.A: McGraw-Hill 2000 # Licker, Mark P. McGraw Hill: Concise Encyclopedia of Physics The Lakeside Press The McGraw Hill Companies, Inc. 2002 # Chappel, Michale A-Z Physics United Kingdom: McGraw Hill 1997, 2000, 2003 # http://www.ph.rhbnc.ac.uk/schools/ZeroT/Absolute.html # Microsoft® Encarta® Encyclopedia 2002. © 1993-2001 Microsoft Corporation. (Encyclopedia CD-ROM # Lazar, A. Miriam Let's Review: The Physical Setting U.S.A. Barron's Educational Series, INC. 2002 'References' # Calle, Carlos A Guide to Physics Bristol and Philadelphia: Institute of Physics Publishing 2001 # http://csep10.phys.utk.edu/guidry/violence/bang2.html # http://www.colorado.edu/physics/2000/bec/temperature.html # http://www.pa.msu.edu/sciencet/ask_st/012992.html # http://en.wikipedia.org/wiki/Uncertainty_principle # http://en.wikipedia.org/wiki/Absolute_zero # http://en.wikipedia.org/wiki/Third_law_of_thermodynamics # http://en.wikipedia.org/wiki/Cryogenics